This application claims the priority of German Patent Document No. 103 50 727.2, filed 30 Oct. 2003, the disclosure of which is expressly incorporated by reference therein.
This invention relates to a component with a platinum-aluminum substrate area, in particular a component of a gas turbine. In addition, this invention also relates to a platinum-aluminum coating and a method of producing such a component.
European Patent 0 784 104 B1 relates to a superalloy based on nickel with an optimized platinum-aluminum coating. This prior art discloses an object having a platinum-aluminum surface region, where a nickel-based substrate has first platinum and then aluminum diffused into the substrate surface. This provides a substrate surface region having an integrated aluminum content of 18 to 24 wt % and an integrated platinum content of 18 to 45 wt %, with the remainder comprising constituents of the substrate mass composition. The platinum content and the aluminum content are relatively high in the area adjacent to the substrate surface, decreasing with an increase in the distance from the substrate surface into the substrate. According to European Patent 0 784 104 B1, the integrated values for the aluminum content and the platinum content of the substrate surface region are determined by an integration method, in which the platinum content and the aluminum content are integrated over the distance from the outer substrate surface. A lower integration limit is approx. 2 to 3 μm below the substrate surface. An upper integration limit is determined by the distance from the substrate surface at which the aluminum content measured in wt % has dropped to a value of 18 wt %, starting from a higher value. This upper integration limit is used for determining the integrated aluminum content and also for determining the integrated platinum content.
The platinum-aluminum coating and/or the component having such a coating disclosed in European Patent 0 784 104 B1 has a low ductility. This low ductility is caused by the relatively high aluminum and platinum contents. Because of this low ductility, components coated in this way have a limited thermomechanical fatigue (TMF) resistance. In the case of the blades of gas turbines that are exposed to cyclic thermomechanical stresses due to changes or fluctuations in operating temperature, cracks may develop in materials of limited TMF resistance. This may lead to breakage of the blades. An object of the present invention is thus to improve the TMF resistance.